E-mail (sometimes spelled email) is the
collective name for messages sent and received over
electronic networks such as the Internet. On the Internet, e-mail is
sent using the Simple Mail Transfer Protocol (SMTP). Local networks
sometimes use different protocols.

One important aspect of e-mail is that the message is sent without
any form of protection. The actual text of the message, as well as
any attachments, can easily be seen by anyone. Many people thus
recommend the use of encryption
to protect e-mail privacy.

Also important to note is that SMTP does not have any authentication
built in. Anyone can send messages that purport to come from someone
else, and it is difficult to reliably determine who the real sender
was. Digital signatures are one
solution to this problem. These are today recognized as legally binding (in Dutch).